Overall, the Helios 44K-4 seems to be the sharpest and most contrasty;
however, it may have a slight edge because of its slightly longer focal
length, which results in slightly greater magnification of the letters,
which might create an illusion of better clarity. Even taking that into
account, I think it's a bit sharper than the others. Next comes the
Chinon, then the Pentax, the Industar, and finally the Tamron. I'm a bit
suspicious of the Tamron's low showing, though; it did much better at 35mm.